Another resident wrote to the Gold Coast City Council in May, expressing similar fears as the family spent winter nights sleeping on a wooden platform in a park. At night the baby could be heard crying.

"Why was the baby left with the parents, just why," the resident, who was not named, told The Gold Coast Bulletin.

The baby's body was found on the shoreline of the Gold Coast beach. (9NEWS)(9NEWS)

Council staff wrote back after five days, telling the resident to raise the matter with other authorities as it was not a council responsibility.

A support worker from homeless services did visit the family but the couple refused help, the Bulletin reported.

Child safety advocate Hetty Johnston says there must be a public inquiry into how the baby was left in such a heart-breaking situation.

"The public needs to understand the system they are paying for and how broken it is," the Bravehearts founder said.

"If they (child services) did know about this family, we need to know what happened here. And if they didn't know, then there's something seriously wrong there."

Locals say they contacted police months ago about the families living conditions but nothing was done. (9News)

The parents were already known police. Queensland's child safety department won't say if it was aware of the family's circumstances.

Queensland police declined to say what action was taken over Ms Sorensen's complaint.

Today, Queensland Police Commissioner Ian Stewart confirmed the baby's brother is being cared for and was safe.

Detectives are trying to determine if the baby was dead before she was found by a passer-by at the water's edge. It's believed she had been in the water at some point.

Meanwhile, NSW Police are looking at the couple's movements in the Tweed Heads area, on the border with Queensland, where they were also known to have been sleeping rough.

Queensland police expect to receive the results of an autopsy this afternoon.